FIELD OF THE INVENTION
[0001] This invention relates to a liquid crystal display device, and more particularly
to a color liquid crystal display device suitable for 7-segment numeric display.
BACKGROUND OF THE INVENTION
[0002] In color liquid crystal display devices of the type in which color filters are formed
on matrix electrodes, a liquid crystal television having comb tooth-like electrodes
in the unit pixel of image display is disclosed, for example in Japanese Patent Laid-Open
No. 222877/1984. Since the color liquid crystal display devices use matrix electrodes,
a voltage in either an X direction or a Y direction is applied to those portions which
are not turned on, so that these turn-off portions look as if they were turned on,
depending upon an angle of view.
SUMMARY OF THE INVENTION
[0003] It is a primary object of the present invention to provide a color display device
having excellent visibility by improving contrast.
[0004] The present invention relates to a color liquid crystal display device having color
filters on the surface of comb tooth-like electrodes. In accordance with the present
invention, two comb tooth-like electrodes which are fixed in either X direction or
Y direction are formed for each segment for 7- segment numeric display, for example,
and the color filters are uniformly formed on the entire surface of a display range
in agreement with the direction of the comb tooth-like electrodes. More in detail,
the direction of the teeth of the comb tooth-like segment electrodes is in agreement
with the direction of disposition of the color filters and moreover, the color fifters
are disposed on the entire surface of the display range. If the color filters are
disposed on only the segment electrodes, the turn-off segment electrode portions look
as if they were turned on. To solve this problem, the present invention disposes a
dummy filter on the entire surface of the display range and thus provides a color
liquid crystal display device having high contrast and excellent visibility.
BRIEF DESCRIPTION OF THE DRAWINGS
[0005]
Fig. 1 is a plan view showing the relation of patterns between upper and lower electrodes
and also a display plate as a whole;
Fig. 2 is a schematic view showing a display example of a liquid crystal display device
to which the present invention is applied;
Fig. 3 is an enlarged sectional view of the principal portions of the liquid crystal
display device in accordance with one embodiment of the present invention;
Fig. 4 is an enlarged view of the principal portions and is useful for explaining
the relation between the electrode patterns shown in Fig. 1 and a color filter;
Fig. 5 is an explanatory view useful for explaining the relation of transparent electrodes
in the present invention;
Fig. 6 is a plan view showing the electrode pattern in another embodiment of the present
invention;
Fig. 7 is an enlarged view of the principal portions and is useful for explaining
the relation between the electrode pattern shown in Fig. 6 and the color filter;
Fig. 8 is an enlarged sectional view of the principal portions of the liquid crystal
display device in accordance with still another embodiment of the present invention;
and
Fig. 9 is a partial, enlarged plan view of the liquid crystal display device shown
in Fig. 9.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0006] In the accompanying drawings, Fig. 2 shows an example of the display content of a
speed indicator using a liquid crystal display device. The numeric unit consists of
seven segments, which are hereby called "a, b, c, d, e, f and g segments".
[0007] Referring to Fig. 3, segment display electrodes 13 are disposed on a glass substrate
11 of a lower plate, and color filters such as red and green filters 14R and 14G are
alternately formed on the segment display electrodes 13. On the other hand, a flat
electrode 12 is disposed on the lower surface of a glass substrate 10 of an upper
plate that faces the lower plate glass substrate 11. The flat electrode 12 has a 7-segment
shape such as shown in Fig. 1. Orientation control films 15 are formed on the color
filters 14R, 14G and the flat electrode 12 in order to orient the liquid crystal molecules
in a certain predetermined direction, and a liquid crystal material 18 is sealed between
them. A lower plate polarizer 17 is disposed by an adhesive outside the lower plate
glass substrate 11 while an upper plate polarizer 16 is disposed by an adhesive outside
the upper plate glass substrate 10.
[0008] When a square wave voltage is applied to each of the flat and segment display electrodes
12, 13, the liquid crystal 18 at the portions where the flat electrode 12 and the
segment display electrodes 13 overlap with one another moves so that each color of
the color filters 14 can be seen through. Here, three colors, that is, the color of
the filter itself, monochrome and their intermediate color, can be displayed by selecting
a voltage to be applied to the segment display electrode 13.
[0009] In order to obtain higher contrast and to improve visibility, further, the present
invention employs an electrode pattern construction such as shown in Fig. 1. In Fig.
1, the pattern represented by solid line indicates the segment display electrode 13
and the pattern represented by dash line does the flat electrode 12.
[0010] The segments a, b, c, d, e, f and g are formed on the segment display electrode 13
by comb tooth-like electrodes that are all coordinated in a longitudinal direction
with respect to a display segment. Fig. 5 is a partial enlarged view of the g segment.
Incidentally, for the sake of convenience. of forming the color filter, the comb tooth-like
electrode corresponding to the same color in each segment is positioned on the same
line in a stripe direction. In other words, the comb tooth-like electrode of the a
segment corresponding to R, for example, is disposed on the same line in the longitudinal
direction as the comb tooth-like electrodes of the b, c, d, e, f and g segments corresponding
to R.
[0011] Since the pattern display of the liquid crystal display device by the application
of the voltage to the electrodes 12, 13 is effected by the peripheral portion of the
flat electrode 12, which does not make segment display, rather than the segment display
electrode 13, it is generally effective if the occupying area of the flat electrode
12 than the occupying area of the segment display electrode 13 which includes the
gap portion between 13gR and 13gG as shown in Fig. 5.
[0012] The flat electrode 12 represented by dash line in Fig. 1 defines the shape of the
7-segment display pattern. As to the b and f segments and the c and e segments whose
longitudinal direction is in agreement with the stripe direction, the segments are
connected with one another inside the 7-segment. As to the other segments that can
be formed in a size greater than the display segments, that is, the a, d and g segments,
either one of the end portions of each segment in its longitudinal direction is used
as an extension portion for mutual connection of the electrodes. The extension patterns
are connected integrally inside an effective display range 20 as the liquid crystal
display device (inside one-dot-chain line in Fig. 1) and moreover, while the wiring
of the extension pattern of the segment display electrode 13 is outside the effective
display range 20 when the lower plate glass substrate and the upper plate glass substrate
are superposed with each other.
[0013] The connection arrangement described above can prevent turn-on of the turn-off portions
due to the crossing of the wirings of the extension patterns of the upper and lower
transparent electrodes other than the turn-on shape portions within the effective
display range, and can reduce and simplify the wirings.
[0014] When a plurality of flat electrodes A, B facing one another in the X direction are
connected in the shortest distance as shown in Fig. 1, it is advantages for the wiring
arrangement to employ the relation W
A , W
B > W
A', W
B' where A', B' are segment electrodes facing the flat electrodes A, B and W
A' and W
e' are the width of the segment electrodes A' and B', respectively. From the aspect
of the relation of the areas between the flat electrode and the segment display electrode
described already and for the determination of the display pattern, it is advantageous
to employ the relation L
A', L
8' > L
A, L
B where L
A and L
B are the length of W
A and W
e in the Y direction and L
A' and L
B' are the length of W
A' and Wε' in the Y direction.
[0015] In accordance with the present invention, the display unit can be driven completely
statically and display having high visibility without any dependence on the angle
of view can be accomplished.
[0016] Fig. 4 shows the case where a color filters 14 are formed on the electrode pattern
shown in Fig. 1. The red and green stripe-like color filters are alternately formed
in the longitudinal direction which is the same direction of the comb tooth-like electrode
pattern, and uniformly over the entire surface of the effective display range.
[0017] According to this embodiment, the entire surface of the effective display range becomes
uniform and since the color arrangement of the turn-off segment portion is exactly
the same as that of the portions outside the display unit, display having high visibility
can be provided.
[0018] Fig. 6 shows the case where the stripe direction of the comb tooth-like electrodes
is transverse with respect to the display segments. In this case, all the segment
display electrodes 13 are in the transverse direction. As to the condition of formation
of the terminal portions, the shape of the terminal portions of the b, c, e and f
segments in Fig. 1 corresponds to the a, d and g segments in Fig. 6, and the end portion
of each segment is formed in the transverse direction. The shapes of the terminal
portions of the a, d and g segments in Fig. 1 correspond to those of the b, c, e and
g segments and are formed by the periphery of one side of each segment. Though the
flat electrode 12 is connected to the b and f segments and the c and e segments in
Fig. 1, the three segments, i.e., a, g and d, are connected this time, and the extension
portions of the b, c, e and f segments are disposed at one of the end portions in
the longitudinal direction relative to the display segment. Fig. 7 shows the case
where color filters 14 are formed on the electrode pattern shown in Fig. 6. In the
same way as in Fig. 5, the two stripe-like color filters are formed alternately and
uniformly in the transverse direction with respect to the display segment.
[0019] In a color liquid display device consisting of comb tooth-like electrodes and color
filters corresponding to the electrodes, the present invention can drive the display
device completely statically, can eliminate the occurrence of turn-on of the electrode
patterns other than the pattern of the turn-on portions, and can provide a color liquid
crystal display device having high visibility due to the improvement in contrast.
[0020] In Fig. 8, a segment display electrode 13 is shown disposed on the lower plate glass
substrate 11, and stripe-like color filter layers 14R, 14G for producing display colors
such as red and green are alternately formed on the segment display electrode 13.
Besides the color filters 14R, 14G formed on the segment display electrode 13, a stripe-like
color filter layer 5 for controlling the background color of the liquid crystal display
device 1 is disposed between the color filters 14R and 14G, for example. Since it
is not associated with the turn-on segments, the color filter 5 is formed in a range
other than the segment display electrode 13. An arbitrary color is used for the color
filter 5 so that the desired background color of the liquid crystal display device
1 is determined by the combination of the color filters 14R and 14G for producing
the turn-on colors. In this embodiment, since the turn-on colors are red and green,
the color of the color filter 5 determining the background color is blue. In this
case, the background color by the combination of these solors is substantially approximate
to white.
[0021] On the other hand, the flat electrode 7 is disposed on the upper plate glass substrate
10 in such a manner as to face the lower plate glass substrate 11. The flat electrode
7 has the same of the turn-on segment shown in Fig. 2. Orientation control films 15
for orienting the liquid crystal molecules in a certain predetermined direction are
formed on the color filters 14R, 14G, on 5 and on the flat electrode 12, respectively,
and a liquid crystal material is sealed between these members. The lower plate polarizer
17 is bonded outside the lower plate glass substrate 11 while the upper plate polarizer
16 is bonded outside the upper plate glass substrate 10.
[0022] When a square wave voltage is applied to each of the segment display and flat electrodes
13, 12, the liquid crystal existing between the mutually overlapping electrodes operates
and the color of each color filter 14R, 14G can be seen through. On the other hand,
the liquid crystal 18 at the other portions is inoperative and can be seen through
as the background color other than the color of the turn-on display shape.
[0023] Fig. 9 is a schematic view when the construction of the present invention is viewed
from the side of the liquid crystal display surface. This drawing is a partial enlarged
view of the g segment shown in Fig. 1. Dash line represents the segment display electrode
13 on the lower plate side. The portion colored by the red filter layer 14R is 13gR
and the portion colored by the green filter layer 14G is 13gG. The blue filter layer
5 is formed between the comb tooth-like electrodes 13gR and 13gG.
[0024] Since the red filter layer 13R, the green filter layer 13G and the blue filter layer
5 are formed on the entire surface of the liquid crystal display device 1 shown in
Fig. 2, the mixed color synthesized by these filter colors is the background color
of the liquid crystal display device 1.
[0025] In accordance with this embodiment, the color filter layer for determining the background
color can be formed in addition to the transparent electrodes associated with turn-on
so that the tone of the background color can be expressed freely in accordance with
a customer's need.
[0026] Incidentally, the color filter layer 5 for determining the background color need
not always be disposed between the red filter layer 14R and the green filter layer
14G. For example, the color filter layer 5 may be disposed in the sequence of the
red filter layer 14R, the green filter layer 14G and then the background color filter
layer 5.
[0027] The present invention can accomplish a color liquid display device which can arbitrarily
change the background color in accordance with a customer's need and has high visibility.
1. In a color liquid crystal display device of the type which includes a pair of transparent
substrates (10, 11) facing each other in parallel, a pair of transparent electrodes
(12, 13) formed on the opposed inner surface sides of said transparent substrates,
color filters formed (14G, 14R) on one of said transparent electrodes (13) in such
a manner as to face the other of said transparent electrodes - (12) and a liquid crystal
(18) interposed between said color filters (14G, 14R) and the other of said transparent
electrodes (12), and in which a voltage is applied to the pair of said transparent
electrodes (12, 13) and color display is effected by controlling the transmission
quantity of said liquid crystal, the improvement wherein:
One of said transparent electrodes (13) is disposed as display segments (a -g) at
part inside the full display range (20) of said color liquid crystal display device
occupied by said transparent electrodes;
said display segment (a -g) consists of two sets of comb tooth-like electrodes (13R,
13G) which are controlled independently of each other and are disposed in such a manner
that their comb portions are in engagement with one another; and
the direction of comb teeth of said comb tooth-like electrodes of all of said display
segments (a -g) are arranged in the same direction.
2. The color liquid crystal display device as defined in claim 1 wherein said electrode
(12) on the side where said display segments are not disposed is shaped in a flat
plate form in conformity with the shape of the display pattern of said display segments,
and said electrodes (12) on the side where said segments are not disposed are commonly
wired outside said display range (20).
3. The color liquid crystal display device as defined in claim 1 wherein, when a plurality
of electrodes (A, B) facing one another on the side where said segments are not disposed
are wired with one another in the shortest distance, the width (WA, WB) of said electrodes (A, B) in an X direction is greater than the width (WA', Wa') of electrodes - (A', B') on the side of said segments, which face said electrodes
(A, B) in the X direction, and the length (LA, LB) of said electrodes A, B in a Y direction crossing said X direction at right angles
is smaller than the length (LA', LB ) of said electrodes (A', B') in said Y direction.
4. The color liquid crystal display device as defined in claim 1 wherein two stripe-like
color filter layers (14G, 14R) are alternately arranged as said color filters in the
same direction as the pattern of said comb tooth-like electrodes (13G, 13R).
5. The color liquid crystal display device as defined in claim 4 wherein said color
filters are formed in such a manner as to cover the entire surface of said display
range (20).
6. The color liquid crystal display device as defined in claim 4 wherein a stripe-like
color filter having a color different from the colors of said two color filters is
disposed separately in the proximity of said stripe-like color filters and within
a display range which is not subjected to direct turn-on display control by a control
electrode for controlling said comb tooth-like electrodes and a flat sheet-like electrode
facing said comb tooth-like electrodes, and said separate color filter determines
the backg- roud color of portions other than the portion which is directly displayed
by said electrodes inside said display range.